The control of bovine leukemia virus (BLV) in dairy herds is important in terms of economic loss from export restrictions and carcass condemnation at slaughter in cases which eventually develop lymphoma.
Diagnostic tests for BLV infection include various enzyme-linked immunosorbant assays (ELISA), radioimmunoassays (RIA), and agar gel immunodiffusion (AGID) tests against various viral antigens, as well as viral isolation and viral neutralization tests (Burny et al., 1980, in Klein, G., ed. Viral Oncology, New York: Raven Press, 231-89). The internationally recognized standard test remains the AGID because of its simplicity and low cost. The AGID has been demonstrated to be a useful test for routine herd testing in control programs for the eradication of BLV infection in closed dairy herds (Mammerickx, M. et al., (1978) Ann. Rech. Vet. 9, 885; Van Der Maaten, M.J. and Miller, J.M. (1979) Journal of American Veterinary Medical Association, 175, 1287). However, since BLV infection is subclinical and scheduled blood testing is required to control this disease and for certification of disease free status, many livestock owners do not submit to the cost of routine testing. As well, samples are usually sent to local laboratories where the AGID test results are not routinely available for a minimum of 48 hours.
As there is often considerable delay in obtaining test results there is a need for a simple and better test which could be utilized in situations where results are required as quickly as possible. Such circumstances often exist in sales barns or in calving situations in herds practicing colostrum substitution from BLV free cows. The methodology of the invention can be performed within one hour on samples such as serum or milk.
The test according to this invention is not intended to completely replace laboratory testing but if used on a routine basis it can be the best indicator of current herd status and a powerful tool to assist in herd management for the control and elimination of bovine leukemia virus infection or other infectious diseases. It is the purpose of this invention to be a relatively simple, low-cost, on-site test to monitor cattle and other animals for the presence of antibodies indicating exposure to particular infectious agents. In the instance of bovine leukemia virus the presence of antibodies to the virus has a strong positive correlation with ongoing BLV infection. This invention is a useful tool to determine the infectivity status of cows for purpose or to determine if colostrum replacement should be implemented. It is not the purpose of this test to replace veterinary certification but to assist in the monitoring of herds for the maintenance or development of pathogen-free status.
While the inventive test could be used by qualified experts to certify disease status, lay persons would be equally capable of using this invention to monitor disease and implement control procedures in livestock.